1. Field of the Invention
The present invention relates to a method of detecting any fault of radar apparatus mounted on a vehicle using a movement distance of the vehicle, and a radar apparatus for the same.
2. Description of the Related Art
A radar apparatus mounted on a vehicle is conventionally made a practical use, to detect an obstacle in a relatively short distance. By using the radar apparatus, it is possible to avoid collision of the vehicle with obstacles such as an electric light pole and a block wall when the vehicle is put in a garage.
Also, in recent years, the study for coming to practical use is carried out of a radar apparatus to detect a detection object in relatively long distance in a high speed and in a high precision. By using the radar apparatus, it is possible to prevent the collision of the vehicle with a preceding vehicle. The radar apparatus detects a moving body running at high speed such as a vehicle running in front of the vehicle and a coming vehicle as a main target. Therefore, a detection area is generally set to a relatively narrow range in front of the vehicle.
Also, in such a radar apparatus, it is necessary to carry out a detecting process of a preceding vehicle at high speed in correspondence to the velocity of the vehicle. In this case, the distance measuring range must cover a range from the close distance of tens of centimeters to about hundreds of meters from the vehicle. Therefore, a radar apparatus is proposed in which transmitting means radiates a sharp directional radar beam to the preceding vehicle and receiving means receives a reflected beam from the preceding vehicle.
In U.S. Pat. No. RE 36,095, for example, a multi-beam radar apparatus is proposed which uses a high frequency radio wave beam of a millimeter band. In a radar apparatus of this technique, radar beams are radiated to overlap spatially using a plurality of transmitting and receiving sections, and the combinations of the transmitting and receiving sections are changed to improve the detection precision.
Also, in EP 840,140 A1, for example, a scan beam radar apparatus is proposed which uses a high frequency radio wave beam in the millimeter band as the radar wave. In this technique, the radio wave beam is radiated from a primary emitter and is scanned by a rotating reflector, and a reflection beam from the reflector is converged by a dielectric lens, to reduce an expansion angle. Thus, the radio wave beam is radiated to the front direction of the vehicle.
However, in the multi-beam radar apparatus having a plurality of transmitting sections and a plurality of receiving sections, a peculiar detection area is defined for every combination of the transmitting section and the receiving section. Also, the position of a detection object, i.e., an azimuth angle and a distance from the vehicle are calculated by synthesizing reception signals for the respective combinations of the transmitting section and the receiving section. For this reason, the calculated position of the detection object is different from the actual position of the detection object, when any of the plurality of receiving sections and the plurality of transmitting sections is degraded in sensitivity.
Also, in the scan beam radar apparatus, because a single transmission circuit and a single reception circuit are used, an azimuth angle error is difficult to be generated unlike the above multi-beam radar apparatus. However, the detection sensitivity reduces uniformly over all the azimuth angles due to the degradation of the transmitting circuit or the receiving circuit. Therefore, the distance measuring range for the detection object becomes narrow.
Also, in these conventional radar apparatus, the following matters are necessary to measure sensitivity of the radar apparatus for detection of the degradation of the transmitting or receiving circuit. First, the vehicle with the radar apparatus mounted must be carried to an examination environment in which a reference subject is installed. There, a radar beam is transmitted from an examination location to the stationary reference subject and the reflected signal is received. Thus, the sensitivity of the radar apparatus is detected based on the received signal. Therefore, the regular check is necessary in the conventional radar apparatus. This is inconvenient to the user.
Therefore, an object of the present invention is to provide a method of detecting a fault of a radar apparatus, in which any fault of the radar apparatus mounted on a vehicle can be detected in a usual running state of the vehicle, and a radar apparatus for the same.
Another object of the present invention is to provide a method of detecting a fault of a radar apparatus, in which erroneous detection of a position of a detection object can be avoided, and a radar apparatus for the same.
Still another object of the present invention is to provide a method of detecting a fault of a radar apparatus, in which a detecting operation of any fault of the radar apparatus can be selectively started or stopped, and a radar apparatus for the same.
Yet still another object of the present invention is to provide a method of detecting a fault of a radar apparatus, in which any fault of the radar apparatus can be informed to a passenger of the vehicle, and a radar apparatus for the same.
It is also an object of the present invention to provide a method of detecting a fault of a radar apparatus, in which a detecting operation of any fault of the radar apparatus can be executed to received signals of channels other than fault channels, and a radar apparatus for the same.
Another object of the present invention is to provide a method of detecting a fault of a radar apparatus, in which a detecting operation of any fault of the radar apparatus can be executed based on the detection of a detection object and the movement distance of the vehicle, and a radar apparatus for the same.
Still another object of the present invention is to provide a method of detecting a fault of a radar apparatus, in which a detecting criteria of any fault of the radar apparatus can be changed based on the peripheral circumstance of the running vehicle, and a radar apparatus for the same.
In order to achieve an aspect of the present invention, a radar apparatus mounted on a vehicle includes a detecting section and a fault determining section. The detecting section includes a radar unit and detects a detection object using radar wave radiated from a radar unit toward the detection object and reflected radar wave from the detection target to the radar unit. The fault determining section determines whether any fault has occurred in the radar unit, based on the detecting result of the detection object and a movement distance of the vehicle, and generates a fault detection signal, when it is determined that any fault has occurred in the radar unit.
Here, the radar apparatus mounted on a vehicle may further include a state setting switch operated by a passenger of the vehicle to start or stop the fault determining section.
Also, the radar apparatus mounted on a vehicle may further include an alarm section outputting an alarm in response to the fault detection signal.
Also, the fault determining section is always started when the vehicle is started.
Also, the fault determining section may include a counter and a determining section. The counter counts the movement distance of the vehicle, and the counter is reset in response to the detection of the detection object as the detecting result. The determining section checks whether the counter reaches a predetermined value, and determining that any fault has occurred in the radar unit, to generate the fault detection signal, when the counter reaches the predetermined value.
Also, the fault determining section may include a counter and a determining section. The counter counts the movement distance of the vehicle when a power spectrum of the reflected radar wave does not contain any component with an intensity value larger than a predetermined intensity value. Also, the counter is reset when the power spectrum of the reflected radar wave contains any component with an intensity value larger than the predetermined intensity value. The determining section checks whether the counter reaches a predetermined value, and determining that any fault has occurred in the radar unit, to generate the fault detection signal, when the counter reaches the predetermined value. In the above cases, the fault determining section may further include a distance switch operated by a passenger of the vehicle to set the predetermined value to one of a plurality of distances which are different from each other.
Also, the detecting section may include the radar unit and a position calculating section. The radar unit includes a beam transmitting section radiating the radar wave, and a beam receiving section receiving the reflected radar wave from the detection object. The position calculates section calculating the position of the detection object from the radar wave and the reflected radar wave.
Also, the radar wave includes a plurality of radar beams, and the reflected radar wave includes a plurality of reflected radar beams. In this case, a combination of one of the plurality of radar beams and one of the plurality of reflected radar beams is associated with a channel. Also, the fault determining section determines whether any fault has occurred, for every channel, to generate the fault detection signal.
Also, the radar wave may include a plurality of radar beams, and the reflected radar wave may include a plurality of reflected radar beams. In this case, the radar unit includes a plurality of beam transmitting circuits, each of which radiates the radar beam, and a plurality of beam receiving circuits, each of which receives the reflected radar beam. Also, each of channels is associated with a combination of one of the plurality of beam transmitting circuits and one of the plurality of beam receiving circuits corresponding to the beam transmitting circuit. Or, each channel is associated with a combination of one of the plurality of beam transmitting circuits and one of the plurality of beam receiving circuits adjacent to the beam transmitting circuit. Also, the fault determining section determines whether any fault has occurred, for every channel, to generate the fault detection signal. In this case, the detecting section detects a position of the detection object from a power spectrum of the radar beams and the reflection radar beams for all the channels other than channels specified by the fault detection signals.
Also, the fault determining section includes one of an odometer and a trip meter to output the movement distance. Otherwise, the fault determining section may include a section calculating a velocity of the vehicle using a Doppler shift quantity between the radar wave and the reflected radar wave, and calculating the movement distance of the vehicle based on the calculated velocity and a time.
In order to another aspect of the present invention, a method of detecting a fault in a radar apparatus mounted on a vehicle is achieved by detecting a detection object is using radar wave radiated from a radar apparatus toward the detection object and reflected radar wave from the detection target to the radar apparatus; and determining whether any fault has occurred in the radar unit, based on the detecting result of the detection object and a movement distance of the vehicle, and generating a fault detection signal, when it is determined that any fault has occurred in the radar unit.
Here, the determining operation may be selectively started or stopped. Also, it is desirable that the determining operation is always started when the vehicle is started.
Also, an alarm may be outputted in response to the fault detection signal.
Also, in the determining, the movement distance of the vehicle is counted. The counted value is reset in response to the detecting result of the detection object. It is checked whether the counter reaches a predetermined value. It is determined that any fault has occurred in the radar unit, to generate the fault detection signal, when the counted value reaches the predetermined value.
Also, in the determining, the movement distance of the vehicle is counted when a power spectrum of the reflected radar wave does not contain any component with an intensity value larger than a predetermined intensity value. The counted value is reset when the power spectrum of the reflected radar wave contains any component with an intensity value larger than the predetermined intensity value. It is checked whether the counter reaches a predetermined value, and it is determined that any fault has occurred in the radar unit, to generate the fault detection signal, when the counted value reaches the predetermined value. In the above cases, one of a plurality of distances which are different from each other is selected as the predetermined value.
Also, the radar wave may include a plurality of radar beams, and the reflected radar wave may include a plurality of reflected radar beams. A combination of one of the plurality of radar beams and one of the plurality of reflected radar beams is associated with a channel. In the determination, it is determined whether any fault has occurred, for every channel, to generate the fault detection signal.
Also, the radar wave may include a plurality of radar beams, and the reflected radar wave may include a plurality of reflected radar beams. In this case, each of channels is associated with a combination of one of the plurality of radar beams and one of the plurality of reflected radar beams corresponding to the radar beam. Or, each channel is associated with a combination of one of the plurality of radar beams and one of the plurality of reflected radar beams adjacent to the radar beam. In the determination, it is determined whether any fault has occurred, for every channel, to generate the fault detection signal. In this case, the detection may be accomplished by detecting a position of the detection object from a power spectrum of the radar beams and the reflection radar beams for all the channels other than channels specified by the fault detection signals.
Also, in the determination, a velocity of the vehicle is calculated using a Doppler shift quantity between the radar wave and the reflected radar wave, and the movement distance of the vehicle is calculated based on the calculated velocity and a time.